抄録
The effects of organic food additives on pitting corrosion of aluminum alloys were studied in a neutral solution of sodium chloride. The advance of corrosion was estimated by time variation of the rest potential, anodic and cathodic polarization curves and polarization resistance. Pit depth was evaluated with an optical microscope and photoacoustic spectroscopy (PAS) was newly applied to evaluate the spatial distribution of corrosion pits.
Results obtained were as follows.
1) Organic substances that showed an inhibiting effect, decreasing the maximum pit depth, were: for 3003 alloy DL-thioctic acid, caffein anhydride and L-tryptophan; for 5052 alloy casein; and for 6063 alloy pyridoxine hydrochloride and hydantoin.
2) In the presence of an organic substance as pitting corrosion inhibitor, obtained corrosion potential at pH7 shifted to the noble side, and these results support the evaluated results for the maximum pit depth.
In an acid solution of pH3, obtained corrosion current decreased in the presence of the organic substance. These results suggests the possibility of an inhibitive effect inside the pits as well as outside the pits.
